Related arts are discussed in Japanese Laid-open Patent Publication No. 2005-318479, Japanese Laid-open Patent Publication No. 2009-206852, Japanese Laid-open Patent Publication No. 2006-287906, or Fuketa Hiroshi, Hirairi Koji, Yasufuku Tadashi, Takamiya Makoto, Nomura Masahiro, Shinohara Hirofumi, Sakurai Takayasu, “Energy Efficiency Increase of Integer Unit Enabled by Contention-less Flip-Flops (CLFF) and Separated Supply Voltage between Flip-Flops and Combinational Logics.” IEICE Technical Report, SDM2011-95, ICD2011-63, pp. 127-132, August 2011.